The Influence of Alpha-fetoprotein on Natural Suppressor Cell Activity and Ehrlich Carcinoma Growth

Comprehensive approach to cancer immunotherapy - Simultaneous targeting of myeloid-derived suppressor cells and cancer cells with AFP conjugates

The immune system plays a pivotal role in combating diseases, including cancer, with monocytes emerging as key regulators of immune response dynamics. This article describes a novel strategy for cancer treatment centered on depleting myeloid-derived suppressor cells (MDSCs), to enhance the overall immune response while simultaneously targeting cancer cells directly. Alpha-fetoprotein (AFP) is an oncofetal protein that plays an important role in delivering nutrients to immature monocytes, embryonic, and cancer cells in a targeted manner. AFP can be repurposed, making it a vehicle for delivering toxins, rather than nutrients to kill cancer cells and deplete MDSCs in the tumor microenvironment (TME). Depleting monocytes not only stimulates the immune system but also improves the lymphocyte-to-monocyte ratio (LMR), often low in cancer patients. AFP combined with cytotoxic drugs, offers dual benefit-immune stimulation and targeted chemotherapy. Studies in xenograft models demonstrated high efficacy and safety of AFP-toxin conjugates, surpassing conventional targeted chemotherapy. Such conjugates have also been reported to provide superior efficacy and safety in cancer patients compared to chemotherapy. This approach, using AFP conjugated with toxins, either covalently or non-covalently, presents a safe and highly effective option for cancer immuno/chemotherapy.

Research Progress in Alpha-Fetoprotein-Induced Immunosuppression of Liver Cancer

Abstract:

Liver cancer is one of the most common malignant tumors, with limited treatment and 8.2% high mortality. Liver cancer is the fourth leading cause of cancer-related deaths, which seriously endangers human life and health. Approximately 70% of liver cancer patients show increased serum alpha-fetoprotein (AFP) levels. AFP is the main diagnostic and prognostic indicator of liver cancer. AFP, a key marker of liver cancer, plays a crucial role in regulating the proliferation of tumor cells, apoptosis, and induction of cellular immune escape. High levels of AFP during embryonic development protect the embryos from maternal immune attack. AFP also promotes immune escape of liver cancer cells by inhibiting tumor-infiltrating lymphocytes (TILs), natural killer cells (NK), dendritic cells (DC), and macrophages; thus, it is also used as a target antigen in immunotherapy for liver cancer. AFP is highly expressed in liver cancer cells. In addition to being used in the diagnosis of liver cancer, it has become a target of immunotherapy for liver cancer as a tumor-associated antigen. In immunotherapy, it was also confirmed that early AFP response was positively correlated with the efficacy of immunotherapy. Early AFP responders had longer PFS and OS than non-responders. At present, the methods of immunotherapy for liver cancer mainly include Adoptive Cell Transfer Therapy (ACT), tumor vaccine therapy, immune checkpoint inhibitors (ICIs) therapy and so on. A large number of studies have shown that AFP mainly plays a role in ACT and liver cancer vaccines. This review presents the research progress of AFP and immunosuppression of liver cancer.

The use of alpha-fetoprotein for the treatment of autoimmune diseases and cancer

Alpha-fetoprotein is a shuttle protein that delivers nutrients through receptor-mediated endocytosis to embryotic cells. In adults, alpha-fetoprotein can shuttle drugs into alpha-fetoprotein receptor-positive myeloid-derived suppressor, regenerating and also cancer cells. Drugs with high-binding affinity to alpha-fetoprotein can activate or deplete targeted cells. Myeloid-derived suppressor cells activation leads to immune suppression that can be used for treating autoimmune diseases. On the other hand, toxins delivered by alpha-fetoprotein can damage myeloid-derived suppressor cells and consequently unleash innate and adaptive immunity to destroy cancer cells. Innate immunity natural killers reduce cancer stem cells and metastases. The new alpha-fetoprotein drug noncovalent complexes for immunotherapy change the local immune balance and has potential in oncology, autoimmune and infectious diseases treatment, inflammation, transplantation, vaccination, etc.

Daunorubicin conjugated with alpha-fetoprotein selectively eliminates myeloid-derived suppressor cells (MDSCs) and inhibits experimental tumor growth

Failure of antitumor immunity in cancer was shown to be mediated by myeloid-derived suppressor cells (MDSCs), which are considered to be one of the key factors contributing to the development of malignant diseases. Therefore, the development of pharmacological approaches to effectively eliminate MDSCs in organisms carrying growing tumors is a promising pathway for potential treatment. For this purpose we propose alpha-fetoprotein (AFP) conjugated with a cytotoxic agent as a vector molecule, specifically recognizing MDSCs. The present study was aimed at examination of this suggestion using both in vitro and in vivo approaches. MDSCs, obtained from the spleen of Ehrlich carcinoma bearing mice, selectively bound AFP labeled with fluorescein isothiocyanate. AFP conjugated to daunorubicin (AFP-DR) and DR alone showed similar in vitro cytotoxicity against the granulocytic MDSC subpopulation. The monocytic MDSC subpopulation was resistant to treatment with DR, whereas it was completely depleted in the presence of AFP-DR. Treatment of mice bearing Ehrlich carcinoma with AFP-DR resulted in reduced numbers of splenic MDSCs, normalization of NK cell levels, and inhibition of tumor growth. The obtained results demonstrate that cytotoxic conjugates based on AFP are promising anticancer drugs, which, in addition to the direct effect on tumor cells expressing receptors to AFP, may contribute to elimination of MDSCs.

Tumor-Derived α-Fetoprotein Directly Drives Human Natural Killer-Cell Activation and Subsequent Cell Death

Hepatocellular carcinoma (HCC) patients with reduced natural killer (NK)-cell numbers and function have been shown to have a poor disease outcome. Mechanisms underlying NK-cell deficiency and dysfunction in HCC patients remain largely unresolved. α-Fetoprotein (AFP) is an oncofetal antigen produced by HCC. Previous studies demonstrated that tumor-derived AFP (tAFP) can indirectly impair NK-cell activity by suppressing dendritic cell function. However, a direct tAFP effect on NK cells remains unexplored. The purpose of this study was to examine the ability of cord blood-derived AFP (nAFP) and that of tAFP to directly modulate human NK-cell activity and longevity in vitro Short-term exposure to tAFP and, especially, nAFP proteins induced a unique proinflammatory, IL2-hyperresponsive phenotype in NK cells as measured by IL1β, IL6, and TNF secretion, CD69 upregulation, and enhanced tumor cell killing. In contrast, extended coculture with tAFP, but not nAFP, negatively affected long-term NK-cell viability. NK-cell activation was directly mediated by the AFP protein itself, whereas their viability was affected by hydrophilic components within the low molecular mass cargo that copurified with tAFP. Identification of the distinct impact of circulating tAFP on NK-cell function and viability may be crucial to developing a strategy to ameliorate HCC patient NK-cell functional deficits. Cancer Immunol Res; 5(6); 493-502. ©2017 AACR.

Properties of immature myeloid progenitors with nitric-oxide-dependent immunosuppressive activity isolated from bone marrow of tumor-free mice

Myeloid derived suppressor cells (MDSCs) from tumor-bearing mice are important negative regulators of anti-cancer immune responses, but the role for immature myeloid cells (IMCs) in non-tumor-bearing mice in the regulation of immune responses are poorly described. We studied the immune-suppressive activity of IMCs from the bone marrow (BM) of C57Bl/6 mice and the mechanism(s) by which they inhibit T-cell activation and proliferation. IMCs, isolated from BM by high-speed FACS, inhibited mitogen-induced proliferation of CD4(+) and CD8(+) T-cells in vitro. Cell-to-cell contact of T-cells with viable IMCs was required for suppression. Neither neutralizing antibodies to TGFβ1, nor genetic disruption of indolamine 2,3-dioxygenase, abrogated IMC-mediated suppressive activity. In contrast, suppression of T-cell proliferation was absent in cultures containing IMCs from interferon-γ (IFN-γ) receptor KO mice or T-cells from IFN-γ KO mice (on the C57Bl/6 background). The addition of NO inhibitors to co-cultures of T-cells and IMC significantly reduced the suppressive activity of IMCs. IFN-γ signaling between T-cells and IMCs induced paracrine Nitric Oxide (NO) release in culture, and the degree of inhibition of T-cell proliferation was proportional to NO levels. The suppressive activity of IMCs from the bone marrow of tumor-free mice was comparable with MDSCs from BALB/c bearing mice 4T1 mammary tumors. These results indicate that IMCs have a role in regulating T-cell activation and proliferation in the BM microenvironment.